The present invention relates to penalty brake control systems for railway service and particularly to a reset arrangement for releasing a penalty initiated brake application when a non self-lapping type brake valve device is employed.
Typical penalty brake control systems employ a standard P-2-A type penalty brake application valve device in conjunction with safety monitoring devices to enforce an automatic penalty brake application in the event the operator fails to periodically acknowledge his alertness and well being (safety control) or the train speed exceeds a predetermined safe limit (overspeed and/or train control).
Due to the recent trend toward modern locomotive cab design, the standard 26-C type pedestal-mounted brake valve has been modified for "desk-style" mounting. The concept of this new family of brake valves, designated as 30-type brake valves, initially employed a self-lapping automatic brake regulating valve, as its basis, this feature being similar to that of the standard 26-C brake valve. However, the 30-type brake valves do not carry over the penalty interlock arrangement, in which the "lockover" port of the penalty application valve is controlled through the suppression valve of the 26-C brake valve. Instead, the "lockover" port is controlled via a pneumatic switching valve that is separate from the brake valve and which is piloted by pressure from the brake valve via a suppression pipe when the brake valve is moved to suppression position. Piloting the switching valve effects closure of the "lockover" port, to allow pressure buildup in the control chamber of the penalty application valve for reset and release of the penalty brake application.
More recently, these 30-type brake valves have been expanded to utilize a non self-lapping type regulating valve which requires the operator to move the brake valve handle out of service position to lap position when the desired brake application is obtained. This makes it possible to add a holding position in which an electropneumatic valve in the brake cylinder exhaust line may be energized via a train line wire to hold the brake pressure while re-charging the train brake pipe. In this expanded design of the 30-type brake valve, however, there is no provision for a suppression position, as such, the intention being to utilize service position to obtain the pressure signal at suppression pipe 26, instead of providing a separate suppression position. This was found to be a problem in attempting to suppress or reset a penalty brake application, because in placing the brake valve handle in service position to obtain the desired suppression pipe signal, a concurrent reduction of brake pipe pressure occurs. Since this suppression pressure signal must be sustained for a period of time sufficient to allow the penalty brake application valve to reset, it is possible to have an undesirable over-reduction of brake pipe pressure.